A cap made of synthetic resin material is often fitted to the mouths of the containers of food seasonings, medicines, cosmetics and so on. For instance, Japanese utility model laid-open publication No. 01-66355 discloses a cap comprising a base cap (primary cap) having an outlet opening in the top wall thereof, a lid member (secondary cap) hinged to the base cap via a reversing hinge, and a slidable plate member slidably engaged to the upper surface of the base cap and provided with a ramp portion for pushing up the lid member and a projection that can engage the inner surface of the reversing hinge so that the lid member can be opened up with a single action simply by sliding the plate member.
According to this previously proposed structure, because an end portion of the plate member for opening up the lid member projects laterally, and the lid member can be opened up by pushing this projecting end of the plate member inward, it is possible that the lid member may be inadvertently opened up by the projecting end of the plate member being pushed while the container is being carded. Also, because the opening end of the lid member and the operating end of the plate member are located on the same side, the content of the container may stick to the finger when the content is dispensed.